1. Field of the Invention
This invention relates to a method for joining textile yarns for restoring their continuity in a winding unit, in particular a bobbin winding unit, in which the individual joining operations are independent of each other, and of automatic and flexible implementation.
2. Description of the Art
As is well known, a yarn produced in a spinning machine, particularly a ring spinning machine, is normally wound onto a tube and conveyed as a yarn package to a bobbin winding unit. Because of the limitations of a ring spinning machine, the yarn packages contain a relatively small quantity of yarn, of about a few hundred grams at most.
Consequently they are unwound and then rewound into bobbins in which the yarn quantity is very large, consequently for forming the bobbin some tens of packages are required, so that on changing the package the yarn has to be knotted or joined, after which the known rewinding of the yarn from the new package commences. In an automatic bobbin winding unit used for this rewinding, if a particularly thick or thin portion appears, a procedure is undergone by which the thick portion or the like is detected by a yarn clearer provided in the winding station, the yarn then being totally cut through and the yarn defect removed, after which the yarn is knotted or joined and yarn rewinding recommences. The combination of yarn defects and package changing results in very frequent yarn joining. In particular, if a bobbin carrying a fixed quantity of wound yarn has a large number of knotted joints, these joints must be perfectly made otherwise they can be intercepted by the eye of a needle or of a heddle in the subsequent operation of a knitting machine or loom, resulting in yarn breakage and the requirement for frequent yarn joining, with a low final product production rate. Relatively frequent yarn joining during rewinding additionally implies a low bobbin formation efficiency because of the continual repeating of the knotting cycle. Consequently the knotting cycle has to be as short as possible while at the same time producing acceptable quality. It should be noted that if yarn joints are not of acceptable quality, the bobbins produced are unacceptable in that it is almost impossible for an operator to distinguish these with the eye in a knitting or weaving operation, resulting in a disconcerting deterioration in the subsequent stages of the article production process. To overcome these and other drawbacks, the applicant has experimented with a textile yarn joining method for restoring continuity each time the yarn breaks, or is cut by the yarn clearer, or when the package is empty, said method having proved perfectly reliable in effecting rapid and accurate joining cycles. Hence the present invention not only substantially increases wound yarn bobbin production but also ensures correct yarn behaviour during automatic bobbin winding.